Short wave radio communication system



Sept. 26, 1939. MATHIEU 2,173,911

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Sept. 26, 1939. G. A. MATHIEU 2,173,911

SHORT WAVE RADIO COMMUNICATION SYSTEM Original Filed Oct. 25, 1932 6 Sheets-Sheet 3 N K IPDII i i 1 Sept. 26, 1939.

G. A. MATHIEU SHORT WAVE RADIO COMMUNICATION SYSTEII Original Filed Oct. 25, 1932 6 Sheets-Sheet 4 T RFR 2A rm J 70 rkAusMlrrm L m METER v T km 24 rm J r0 TRANSMITTER RFR ,A r I 9 Y I L l 70 METER Ll b2 RFR //r+ 24 I, 77R GRID w 70 TRANSMITTER TUNE/ab; i2 7;

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s. A. MATHIEU SHORT WAVE RADIO COMMUNICATION SYSTEM Original Filed 001:. 25, 1932 6 Sheets-Sheet 5 PMZ'E LEAD 62 lD/NG CONDUCTOR /ARRAA IGEMEN 7" INVENTOR GASTON AD'ELlN MATHIEU m ATTORNEY Sept. 26, 1939.

G. A. MATHIEU SHORT WAVE RADIO COMMUNICATION .SYSTEM Original Filed Oct. 6 Shets-Sheet 6 2 a R IT u R. .R m T a u u wv n RH R k R W m n w n m T 1 TJTI A A I'M... 2 MT Z n EU I 60 M ED 5. 1 MW m R U RA 3 m mw 7 CE C l i E u H 1 RE R ml 1 W F If ll s r N 4 LOCAL HIGH FREQUENCY 0867i [/1 TOR ZPF LOW PASS FILTER.

INVENTOR GASTON ADELIN MATHIEU Kg ATT ORNEY Patented Sept. 26, 1939 UNITED STATES SHORT WAVE RADIO C'OMIVIUNIGATION SYSTEM Gaston Adelin Mathieu, London, England, assignor to Radio Corporation of America, a corporation of Delaware Original application October 25, 1932, Serial, No 639,462. Divided and this application Junefiii,

1936, Serial No. 86,715. In

vember 5, 1931 8 Claims.

This application is a division of my copending application, Serial No. 639,462, filed October 25, 1932, which has issued as United States Patent No. 2,064,481, granted December 15, 1936.

This invention relates to short wave radio communication systems and thermionic valve constructions for use therein. More particularly, though not exclusively, the invention relates to very short wave systems operating on the so-called braking field or Barkhausen-Kurz principle wherein, as is well known, a thermionic valve is utilized as an oscillator by making the control electrode highly positive with regard to the cathode and maintaining the anode at a potential which is the same as the cathode potential or which may be slightly positive or slightly negative with respect thereto.

As will readily be appreciated, many practical difficulties are experienced in and in connection with ultra short wave transmitters of this type, two of the main difficulties being that of transferring the oscillatory energy within the valve or valves employed to an antenna in an efficient manner and radiating the very short wave energy efliciently from the antenna. A further diificulty lies in the actual construction of the transmitter, this difficulty arising by reason of the very small permissible dimensions of the electrodes employed to produce the very short wavelengths. A still further difi'iculty arises by .reason of the fact that it is practically impossible, or at any rate exceedingly diiiicult, to earth such an ultra short wave transmitter or receiver satisfactorily since in practice an earth wire, which is of negligible length as compared tothe very short working wavelength, is difilcult, if not impossible, to obtain. The last mentioned difficulty has, in part, been met by the employment of the dipole or doublet type of antenna, the said antenna being connected to the thermionic oscillatory system through a Lecher wire system, one-half of the antenna being joined to the plate and the other to the grid point in each case via the Lecher wires. Even with this arrangement, however, difficulties arise because the phasing of the antenna currents is not usually perfect since in a transmitter the grid side of the, doublet has to perform most of the useful work, while in a receiver the heavier share of the work is performed by the anode side of the doublet.

So far as the construction of ultra short wave aerial systems of the doublet type is concerned, attention is directed to my United States Patent No. 2,049,070, granted July 28, 1936, which de- Gteat Britain n6- scribes an invention according to which a skeleton type aerial. comprises a pluralityof rod-like radiators or aerial members supported solely substantially at their middle points (where volt.- age nodes occur) the ends of the rod-like radiators being free in space.

The presentinvention and the invention contained in my United States patent, above referred to, are both concerned with the finding of a practical commercial'applicable solution of the difficulties arisingv in ultra short Wavetransmitting and receiving systems and the two inventions in question may, with considerable advantage, be employed in corribination.

The invention is illustrated in the accompanying drawings.

Fig. 1 illustrates, diagrammatically, one form of transmitting circuit;

Fig. 2 shows a preferrred practical arrangement whereby high tension supply may befed to the grids of the valves in a transmitter in accordance with this invention;

Fig. 3 is illustrative-of an alternative method of feeding high tension to the grids of the valves;

Fig. 4 and Fig; 4a illustrate a suitable constructional arrangement. of valves for use in a transmitter, as illustrated diagrammatically in Fig- 1;

Fig. 5 shows an arrangement wherein filament connecting'Lecher' wires areemployed to couple together two push-pull oscillators in synchronismand in 'isochronism or any other'desired phase relationship;

Fig. 5a. shows a modification of ment of Fig. '5;

Fig. 6 shows an arrangement in which four oscillators in synchronism are employed;

Fig. 7 shows, in diagrammatic detail, a preferred form of receiver;

Figs. 8, 8a and 8b are illustrative of a method of combining a plurality of doublets in a multiple aerial reflector system;

Fig. 9 illustrates a preferred and somewhat modified form of the transmitter shown in Fig. 1 of the drawings; d

Fig. 10 shows, in elevation, and Fig. 11 in end View, a construction of the valve in which the difficulty of the introduction of small extra length wires in the plate circuit is avoided;

Fig. 12 shows schematically a pair of valves arrranged'tooperate as the valves V1, V2 of the transmitter, as illustrated in Fig. 1 of the drawings;

Fig. 13 shows an eflicient arrangement of aerial and associated reflectors, wherein one aerial is the arrangelocated in front of and centrally between two reflectors;

Fig. 14 shows a preferred aerial arrangement of combined transmitter and receiver station;

Fig. 15 shows a receiver corresponding closely in general arrangement to the transmitter of Fig. 9.

Referring to Fig. 1 of. the drawings, the radiating element consists of a doublet antenna A constituted by a copper or slivered copper rod, preferably terminated by discs in and In which serve to reduce the damping of the doublet and to ensure a more uniform distribution of current than would otherwise be possible. The members In and b; may, if desired, be in line with rods and need not necessarily be constituted by circular discs. The doublet is energized from valves V1, V2 constiuting a push-pull connected oscillator. The two sides or halves of the radiating doublet are connected to the grids of the valves, as shown, through the two wires of a Lecher wire feeder, f1, f2, the distances between the connection points of these feeder wires with the doublet and the center point of said doublet being so chosen that the surge impedance of. the feeder f1, is is matched. This surge impedance, of course, depends, inter alia, upon the diameter and distance apart of the component wires of the feeder f1, f2 and if maximum transfer of energy from the valves to the doublet is to be obtained, this surge impedance must be matched to the valves and to the doublet. The Lecher wire feeder f1, f2 is employed as an impedance transformer to ensure the maximum transfer of energy from the oscillator to the antenna and the said feeder will therefore usually be less than one wavelength long. High tension supply to the grids of the valves is applied from a battery or other source Eg through an indicating meter and a variable resistance R1 to the center point of the doublet. The anodes of the valves V1, V2 are joined together by a very short lead of predetermined and preferably adjustable length (this length in conjunction with the inter-electrode capacity of the anodes of the valves V1 and V2 plays an important part in determining the tuning) and the cathodes are joined by a very short lead, as shown in the Fig. 1 now being described. The length of the wire joining the anodes is found to be critical since it is necessary to obtain the correct phase relationship between the high frequency potentials on the two anodes and to ensure that the potentials on the two halves of the dipole shall be exactly out of phase.

When using valves in which the anode connections are brought through the stem with the filament leads, the two short leads may be constituted each by a metal plate, the two plates being arranged close to one another and underneath the valve sockets or mountings, in such manner that they together constitute not merely the short leads but also a condenser d. g is a copper tube which is soldered, or otherwise suitably fixed, to the filament connecting plate of the condenser d and is employed as a support for the whole or part of the transmitter, the said tube also being employed to contain any insulated wire or wires leading to the electrodes of the valves for applying direct current potentials thereto. This method of housing direct current feeding wires results in effective shielding and also protects the wires from being moved about by wind or similar extraneous forces. 7

The other ends of the cathodes are prolonged into the Lecher wires f3, f4, the Lecher wires being adjusted to be suitable for the working wavelength. The filaments are heated from batteries Efl and Efz (which batteries may be, if desired, constituted by a single battery) earthed at one side and connected on the other through variable resistances R2, R3 to movable tapping points upon the Lecher wires. The filament Lecher wires are prolonged beyond the supply points for approximately one-quarter of the Working wavelength so as to ensure the existence of a current loop at that point. Alternatively, the necessity for prolonging the Lecher wires may be avoided by connecting a comparatively large condenser across the supply points. The tube g is earthed through a variable tapping point as shown.

It will be appreciated that the arrangement of the circuit for the filaments results in their being supplied with energy at a nodal point of potential.

The anodes of the valves V1, V2 are connected through a lead it and a suitable indicating instrument to one end of the secondary of a transformer TTl, the other end of the secondary being connected through a battery Ep to earth. Modulating potentials are applied to the primary of the transformer Tn.

A preferred arrangement for feeding high tension supply to the grids of the valves is illustrated in Fig. 2 of the drawings, in which figure the doublet A is shown as supported by a metal pillar a fixed to an insulating block b which is itself supported upon a copper tube C which serves to support the antenna system within the reflector system. The block b may be slid along the tube C and clamped in any position for the purpose of moving the doublet A into the correct focal line position, assuming the reflector (not shown) to be a parabolic reflector as described in our previous specification. The high tension conductor (shown schematically for convenience in drawing at the top of Fig. l) for supplying grid potential is actually passed up through the tube g, from which it is insulated, and on emerging from the said tube g (Fig. 1) is continued up through the plates of the condenser d (the two plates of the condenser 01 are formed with apertures to permit the passage of. the insulated high tension wire) and then through the copper tube C of Fig. 2 whence it is connected as shown to the supporting pillar a. The high tension circuit is thence completed via the doublet antenna itself and the feeder wires f1, f2, as represented diagrammatically in the said Fig. 1. In this manner mechanical rigidity and a high degree of screening is obtained. In the alternative arrangement of grid high tension feed supply illustrated in Fig. 3, the high tension supply is taken to a point between two chokes interposed in a lead connecting the grids of the valves together, and condensers c1, 02 are inserted, as shown, in the feeder wires f1, f2. This connection system permits of the electrical center of the doublet being arranged as shown in the said Fig. 3 and of the insertion of a thermo-couple or radio frequency meter in the center point of the doublet to facilitate correct adjustment of the transmit ter. As will be obvious, the positions of the condensers c1, c2 and radio frequency blocking chokes are capable of considerable variation from that shown in the Fig. 3 now being described.

The doublet antenna with its insert thermo couple or other indicating meter and a considerable portion of the feeder f1, f2 may be mounted within a glass or other suitable container to protect it from the weather, and the remainder of the transmitter may be enclosed in a weather proof box into which the glass container or the feeder alone fits with a moisture proof insulating joint. The screening box should, of course, be so constructed and arranged that it does not give rise to interference effects by reflection of energy.

Alternatively, in place of using an enclosing protective box, the antenna and feeder may be coated with a layer of cellulose or similar protecting varnish or enamel. It is also of advantage to provide such a protective coating to the reflector associated with the system.

Fig. 4 illustrates in perspective elevation, and Fig. 4a in schematic sectional plan taken in the plane of the filaments, one possible form of construction and arrangement of the valves V1, V2, which valves should be arranged side by side and as shown in Fig. 4, so that the leads from each electrode of a valve may be made equal to the corresponding leads from the other valve, the arrangement of the electrodes and leads being symmetrical about a plane equidistant between the two valves. It will be seen that the valves are not alike and are not interchangeable in position if best results are to be obtained, i. e., if the symmertical arrangement shown in the said Figs. 4 and 4a is to be maintained. Starting from this central plane and reading outwards there are first the plate supports PS, then the leads to the rear ends RE of the filaments (i. e. the ends farthest from an observer in Fig. 4) then the leads to the high potential ends HP of the filaments and lastly the grid supports GS. One of the plate supports PS of each valve is continued and connected to leading out wires PSW which leave the valves near the filament'leads REW and I-IPW, the above mentioned relative positions being maintained. The plates are supported at each end by insulated supports PS only one of which, namely that near the low potential end RE of the filament, is continued electrically to form the connecting lead PSW. So long as the symmetrical arrangement is accurately maintained, reversal of the filament lead position is not of much importance, and, of course, the low potential end of each filament must be earthed.

The grid supports GS (as will be seen there are two) are also insulated from each other, the grid connection GSW in'each case being brought out through the valve envelope from the end of the grid adjacent the high potential end HP of the filament. As will be seen, two grid supports and also the two plate supports are insulated from one another by glass beads so that neither the plate nor the grid of either valve has its ends connected together through these supports. For reasons described later, the grid connections may be brought out on each side of the valve, i. e., one lead from each end of the grid.

Alternatively, the separate support and lead for the high potential end of the filament may be provided at the bottom of each valve, it being necessary to arrange that the capacities between the high potential ends of the filaments and their leading out wires and the plates and low potential ends of the filaments should be very small.

For wavelengths of say between 30 and centimeters, two separate valves may economically be employed, but for shorter wavelengths it will possibly be found necessary to locate the electrode system constituting the two valves side by'side in one envelope so'as'to avoid'the difficulty of obtaining the very short in'ten'ionnections necessary with such very short wavelengths.

Numerous modifications as to the manner in which modulation is effected may be made. In the case of Fig. 1 already described, modulation is effected by means of a transformer TM in series with the plate circuit of the valves, this transformer being, of course, of low ohmic resistancein its secondary windings to avoid reducing the power of the transmitter. The amount of modulation power required with this method is very small and the application of a correct value of negative potential to the plates is an important factor in determining quality.

An alternative method of modulation is by varying the high tension supply to the grids of the-valves by means of a powerful amplifier connected through a transformer whose secondary is in series with the supply leads.

Yet another method of effecting modulation is by the application of low frequency push-pull modulation in the plate or grid circuit of the oscillator.

In the former case (i. e. push-pull modulation in the plate circuit) the plate circuit is split and two suitable condensers inserted in series, leads being brought from across these two condensers to the secondary winding-of a modulation transformer, the high tension supply being, of course, fed to the center point of this winding. In the latter case (i. e., push-pull modulation in the grid circuit) the said grid circuit is analogously arranged by splitting the antenna at its center point and inserting a large condenser or two'condensers in series to permit of the insertion of the secondary winding of a push-pull transformer across them, the high tension supply being, of course, fed to the middle point of this winding.

With reference to the circuit illustrated in Fig. 1, it should be understood that this circuit is quite satisfactorily operative with half the power, i. e., it will operate successfully if one of the valves is switched off (or burnt out) or is replaced by the equivalent capacity network. In general, however, maximum output Will be required and the two valves in push-pull should be employed.

Obviously, reception can be achieved by arrangements as already described by providing means for listening in the modulating circuits. It is preferred, however, to employ a special arrangement for receiving, which arrangement will be described later with reference to Fig. '7.

Fig. 9 of the accompanying drawings illustrates diagrammatically and schematically a preferred and somewhat modified form of the transmitter shown in Fig. 1 of the drawings.

It will be noted that the arrangement of Fig. 9 differs from that of Fig. 1 of the drawings, principally in. the arrangement of the filament circuit and that four main tuning adjustments are provided as indicated at l, 2, 3 and 4. These four adjustments are: adjustment l of the length of the Lecher wire feeder f1, f2 connecting the grids of the valves V1, V2 to the aerial. This adjustment, together with adjustment of the distance between the conductors f1, f2, enables the impedance of the feeder constituted by the said conductors to be matched to that of the aerial and the correct terminal conditions obtained; adjustment 2 of the length of the plate conductors f7, fa; adjustment 3 of the conductors f5, is from earth to the earthed ends of the filaments; adjustment 4 of the conductors f3, ii to the ends of the filaments. The correct conditions of tuning, i. e., the proper lengths of conductors (in terms of the working wavelength x) are indicated in Fig. 9. As regards the proper lengths of the leads interconnecting the two plates and interconnecting the earthedl ends of the filaments, those would ordinarily require to be so short that where separate valves of normal dimensions are employed for the valves V1, V2, the constitution of these interconnecting leads would be practically impossible owing to the fact that the envelopes of the valves cause their physical separation by too great a distance. This difficulty can be avoided by increasing the lengths of these interconnections each by one wavelength and bending as much of the added wavelength of conductor as possible each back upon itself, hair-pin fashion, as indicated in the accompanying Fig. 9 so that the said add-ed wavelengths are non-radiating.

In practice, each Lecher wire or hairpin conductor employed for tuning is arranged in a screened earthed copper tube and this enables the tuning systems to be arranged side by side in a screened box without giving rise to undesired couplings.

The frequency of oscillation generated will depend upon the tuning, upon the potentials ap plied to the valves and also upon the dimensions of the plates and grids of the valve. It is found that a fairly wide range of frequencies can be obtained with a given suitable type of valve in a transmitter as illustrated in the accompanying Fig. 1 and in fact a frequency range of 25 x 10 cycles has been obtained. Tuning adjustments 2 and 3 are very critical in determining the frequency generated while tuning adjustments 1 and 4 determine the efiiciency oi the transfer of energy from the valves to the aerial. The shortest wavelength which can be obtained from any particular transmitter is in practice that which is obtained when the proper length of the conductor between the two plates necessary to tune to that wavelength is the smallest practicable length. For shorter wavelengths valves with smaller electrodes and capable of generating at lower grid negative voltages, the limiting frequency obtained with the larger valves must be used. In practice, valves having plates 20 mm. long and 11 mm. diameter have been used for the wavelength range 70-45 cms. (with 300 volts'positive grid potential for 50 cms.) while valves with plates 15 mm. long and 9 mm. in diameter have been used for the range 30-35 cms. (with 175 volts grid positive for 50 cms.).

Although the form of valve shown in Figs. 4 and 4a is a form which can be used, it is found difiicult to obtain satisfactory results from an ultra short wave transmitter as described in the said specification if the valves therein employed are of this form and are fitted with sockets.

The practical necessity to avoid the use of sockets is an obvious serious disadvantage leading to considerable delays in the event of a valve burning out, and moreover involving the risk of upsetting some of the critical adjustments of the circuit in question.

The difiiculties met with in attempting to fit valves, as shown in Figs. 4 and 4a with sockets are due to the fact that the use of such sockets in these valves involves the introduction of a small extra length of wire in the plate lead, this extra length, although quite small, being sufficient to prevent the valves from oscillating.

Fig. 10 shows, in elevation, and Fig. 11 in end view, one construction of valve in which the above mentioned piacticaldifiiculty is avoided, and Fig. 12 shows schematically a pair of valves arranged to operate as the valves V1, V2 of a transmitter as illustrated in Fig. 1 of the drawings. It will be observed that the principal difference between the arrangement of valve illustrated in Figs. 10, 11 and 12, and that illustrated in Figs. 4 and 4a; of the drawings, is that the plate of the valve is completely insulated from the socket, the lead to the plate being brought through the glass bulb. In Figs. 10, 11 and 12, now being described, P represents the plates, G the grids and F the filaments, the plate lead PL being brought through the glass envelope of the valve as shown. As will be seen, the valve sockets are so arranged that the plates do not lie parallel to one another and so the conductors leading to the low potential ends of the plates are brought close together. These conductors indicated at PL1 are either cut off to the correct length (which may be found experimentally) and joined together or, as illustrated in Fig. 12, are connected together through a sliding connector arrangement whereby the effective length of lead between the plate P of one valve and the plate P of the other can be conveniently adjusted. The grid leads are continued into the Lecher wires f1, f2, corresponding to the Lecher wires f1, f2 of Fig. l of the drawings.

' The necessity for distinction in arrangement of the valves between the high and low potential ends of the electrodes and the need for maintaining symmetry apply also to whatever type of valve is employed.

While the length of the connecting leads between the two valves is very critical once it has been determined, it is possible to increase it by integral multiples of half wavelengths and still obtain the benefit of the invention. This allows the valves to be spaced apart more than when the shortest length of connection is used and further allows the envelopes of the valves to be made of larger size, an advantage from the point of view of heat dissipation.

The same types of valve and circuits above described are suitable for receiving purposes. Microphonic noises can be substantially eliminated by mounting the envelopes of the receivin valves in rubber sponge blocks.

Fig. 5 shows two push-pull oscillators consisting of valves V1, V2, V3, V4 coupled together by filament Lecher wires. If the extremities of the filament Lecher wire systems remote from the valves are connected directly together, as shown in the said Fig. 5, and if the said systems are of the correct length, perfect in-phase excitation of the two oscillators can be obtained. Since, of course, the frequency generated by the oscillators depends on small variations in geometric construction, as well as on supply potentials, it is necessary to adjust one oscillator until its wavelength closely approaches that of the other, when the two will pull in step. In practice, this adjustment is best carried out by varying the filament current of each valve separately and keeping the other supply potentials constant. In order to facilitate this, blocking condensers C1, C2, C3, C4 are inserted in the filament Lecher wires as shown, i. e., in that portion of the system which is employed to couple the oscillators together. In Fig. 5, the potential distribution (theoretical) has been indicated by broken lines. In practice, however, the distribution curve probably continues and falls to zero at the earth point. The actual efiect obtained is, however, complex since a portion of the high frequency current passes through the. capacity formedby the leads .to the valves at the: point where they are sealed into the. glass. Fig. 5, however, is illustrative of the manner in. which energy which would otherwise be wastedin the filament Lecher wire .systemmay be utilized for linking together two or more transmitters.

Another method of coupling transmitters in synchronism and. isochronism, or in any other phase relation, is' to prolong the grid circuit of the valves in a direction opposite from' the antenna. For this, of course, connection must be made to both ends of the grids of each valve, this connection being made through the glass envelopes, as previously'explained. In this'way the grids are in efiect prolonged on both sides of the valves into Lecher wire systems, and the rear Lecher wire systems of two or more transmitters are joined together at predetermined points so as to achieve a predetermined phase relationship of coupling.

In. yet another method of coupling two transmitters in synchronism and isochro-nism or in any other desired phase relationship, the grid leads are coupled at a point between the grids of the two valves and the antenna of each transmitter. The arrangement is similar to that shown in Fig. 5, just described, but the use of condensers at each end of the coupling wires is not necessary since the two systems will normally be fed with grid current at the same potential.

Fig. 5a shows a general arrangement of the type hereinafter described.

In carrying out the present invention, Lecher Wire systems to the antenna or for the filaments, or for grid coupling may be wholly or in part replaced by coils of the required equivalent electrical dimensions in order to reduce space where required. Such coils should, of course, be so designed thatthe potential distribution simulates as closely as possible that which obtains in the Lecher wires.

In addition, the Lecher wire systems may be themselves.

Fig. 6 shows a modification or development of the arrangement illustrated in Fig. 5, in which four transmitters are coupled together.

to illustrate a method of coupling. Obviously the invention is not limited to coupling two or four transmitters together, the systems of the said Figs. 5 and 6 being capable of extension almost without limit. Obviously the doubletsin' the separate transmitters which are coupled together in the said Figs. 5 and 6 may be arranged in any required positions to secure required directional eifects. Alternatively, the circuits may 'be adjusted so that the doublets oscillate with a definite predetermined phase difference for" securing desired directional effects. Various methods of combining doublets will be described with reference to Figs; 8, 8a and'SUa'nd' with reference to Figs. 13 and 14 of the accompanying drawings.

Fig. '7 shows oneform of receiver, the construction of which will, it is thought, be fairly obvious from the description already given with .reference to' Fig. .1 of thistspecification: Refer i In the said Fig. 6, as in the said Fig. 5, the circuits are .not shown in full, but only insofar as is necessary ring:toi Fig; 7, A; is a doubletiiantenna which may be an exact duplicate of thatiemployed at the cooperating .transmitter and arranged with discs asillustratedgsaid' discs being? preferably adjustable along their corresponding antenna halves; (The provision of adjustably mounted discs is also to berecommended' inttrans-mitter aerials.) The lengths of the feedersf'r, f'z, have an important influence. on the tuning. of. the receiver andmay be easily made adjustable by constituting them by copper rods. adjustable within copper tubes, as indicated. Maximum signal strength will be obtained when thefeederlength, the antenna length,:andtheposition of the contact points of the'feed'ers on the antenna are such as to give maximumresponsetothe incoming wave and. to provide maximum transfer of energy from the antenna to the valves.

It will be noted, in theFig. 7 now'being'described, that. the plates of the valves V1 and V:

are connected to the doublet antenna", the grids being joined with'short leads of: predetermined and preferably adjustable length (see preceding description with regard to the corresponding leads i It has been found that thisin the transmitter). arrangement gives very goods'ensitivity. Accurate tuning is obtainable. by alteration of the potentials applied to the valve electrodesthe'se adjustments being'efiected in obvious mannerby' the potentiometer'and other'variable resistance devices illustrated in Fig. '7. For telephonic reception, very fine and accurate control of both filament and plate voltages is necessary, and many combinations of potential adjustments are possible for giving good resultsr dition the valves do not easily oscillate; If "an auxiliary oscillator (of widely adjustable fre*-= quency)- be provided; and employed to superim pose 'an e. 'm'. f. on'th'e plates'of the valves, its

effect will be to bring the valvesrapidl'y and al" ternately'to the condition (positive plate potential) for detectionand-tothe conditionmegative" plate potential) for oscillation, and super regenerative reception can therefore-be accomplished. not necessary and quite goodresults can be ob tained without'a local oscillator and with the The principal disadvantagesi-n dispensing with supervalves" biased to the detecting condition.

regeneration are reduced sensitivity and a necessity for somewhat-more-critical adjustment;

The audiooutput'ofthe receiver proper (that However", such super-regeneration isis from-the valvesvl anava) is choke-capacity coupled, as shown, to a succeeding'valve Va ar-- ranged in the ordinary way; Obviously, instead of employing the arrangement shown for the supply of potential to the anodes of the'valves V1,

V'a, this supply may be made through the doublet in a manner analogous to that already described with reference to a transmitter and'illustrated in Fig. 2.

In such an arrangement the anode that the system is stabilized when approaching the point ofoscillations As in the case of a transmitter, one of the 1 valves'vl or V'2 maybe replaced by an equivalent 1 capacity network and receivers maybe coupled together. in a manner; analogous to those already described with reference to the coupling together of transmitters.

Fig. 15 of the accompanying drawings shows a receiver which, as will be seen, corresponds closely in general arrangement to the transmitter shown in the accompanying Fig. 9. Parts in the accompanying Fig. 15 corresponding to parts in the accompanying Fig. 9 are indicated by like reference numerals but with an affixed tick. As will be seen, one main difference is that the plates of the valves Vi, V'z are connected to the aerial A, the grids being coupled via condensers C4, C5 to the primary of a transformer Tr whose secondary feeds (preferably through a low pass filter LPF) into a low frequency amplifier, not shown. The condensers C2, C3, C4, C5 and the chokes CH1, CH2 enable separate readings of the DC grid currents of the two valves to be taken on the instruments I1, 12. A0 is a local oscillator (for super-regeneration) which is variably coupled to the receiver proper as shown, while PA and RA are an adjustable potentiometer and resistance, respectively. The low pass filter eliminates unwanted high frequency due to the oscillator A0.

As in the case of a transmitter where the working wavelength is predetermined and fixed adjustments 3, 4 and I (or 3', 4', I as the case may be) may be dispensed with and fixed values instead of variable values provided.

Referring now to Fig. 8, this shows three doublets I A, 2A and 3A, each having terminating discs which are also employed to couple the doublets together. The doublet IA is connected to a thermo-couple or other rectifier and indicating meter (not shown) to facilitate adjustment to the correct wavelength. The doublet 2A is the transmitter doublet while the doublet 3A is a receiver doublet, the connections for the transmitter and receiver being represented by TTR and RCR, respectively. Any known arrangement of echo suppressor may be arranged in connection with an installation embodying three doublets as illustrated in Fig. 8 now in question, and with the use of a suitable echo suppressor duplex working with a single reflector for both receiving and transmitting is quite practicable.

Fig. 8a is intended to represent the dipole arrangement of a double transmitter consisting of two transmitters coupled together, for example, as illustrated in Fig. 5, a third doublet IA for connection to a meter being interposed between the two transmitting doublets 2A. The doublet IA which may be referred to as a wave meter doublet by reason of the purpose of its provision, may be made to be very sharp in tuning by employing larger discs than are employed on the transmitter doublets, there being, of course, a corresponding reduction in' the length of the dipole or doublet between the discs.

The reason for reducing the length of the wave meter doublet and for increasing the diameter of the discs is that the damping and consequently the absorption of energy, are considerably reduced thereby, while the current at the center of the doubletis increased. This enables a larger instrument reading to be obtained, thus facilitatsorbed by the wave" meter doublet is reduced to a minimum, it does not materially aflzect the amount of power radiated, and, when arranged as shown in Fig. 8a, may actually assist by increasing the effective length of the antenna proper.

In connection with the provision of these wave meter doublets, it may further be noted that the power absorbed by them (which is reduced to a minimum) assists in producing a more uniform current distribution at the focus of the reflector.

In another arrangement the wave meter doublet is mounted in front of or just inside the reflectors.

Fig. 8b represents an installation comprising two coupled transmitter doublets 2A, each of which is coupled to a wave meter doublet IA. One of these wave meter doublets may, of course, be replaced by a receiving doublet.

Instead of arranging the aerial and associated reflectors as rep-resented schematically in Figs. 8, 8a and 8b, just described, considerably better efficiency is obtained by using one aerial in front of and centrally between two reflectors, as shown in the accompanying Fig. 13. A preferred arrangement of combined transmitting and receiving station is shown schematically in the accompanying Fig. 14 in which IA is a receiver doublet and 2A are transmitting doublets.

Throughout Figs. 8, 8a and 8b and the accompanying Figs. 13 and 14, the lines marked RFR represent the central wire of the parabolas forming the reflector.

What is claimed is:

1. In an ultra short wavelength communication circuit, a pair of oscillator tubes connected together in push-pull relation, and another pair of oscillator tubes also connected together in pushpull relationship and generating oscillations approximately the same frequency as said first pair of tubes, said two pairs of oscillator tubes being connected together by a line effectively a whole number of half wavelengths long, whereby predetermined phase excitation of each pair of oscillator tubes with respect to the other pair is obtained, two other pairs of oscillator tubes similarly connected together as said first two pairs, said last two pairs being connected to said first two pairs by a transmission line a whole number of half wavelengths long.

2. In an ultra short wave communication circuit, a pair of oscillator tubes connected together in push-pull relationship, and another pair of oscillator tubes also connected together in pushpull relationship and generating oscillations of approximately the same frequency as said first pair of tubes, each of said tubes including cathodes having two terminals, one cathode terminal of each oscillator tube being connected to a cathode terminal of its associated tube in the same pair, and the remaining cathode terminals of each pair being coupled to similar cathode terminals of the oscillator tubes in the other pair over a line effectively a whole number of half wavelengths long, whereby in-phase excitation of each pair of oscillator tubes with respect to the other pair is obtained.

3. In an ultra short wavelength communication circuit, a pair of oscillator tubes connected together in push-pull relation, and another pair of oscillator tubes also connected together in push-pull relationship and generating oscillations approximately the same frequency as said first pair of tubes, a conductor effectively a whole number of half wavelengths long connecting one terminal of one cathode of said first pair of tubes to a terminal of a cathode of said second pair of tubes, a parallel conductor of similar length connecting together one terminal of the other cathode of said first pair of tubes to a terminal of the other cathode of said second pair of tubes, whereby predetermined phase excitation of each pair of oscillator tubes with respect to the other pair is obtained.

4. In an ultra short Wavelength communication circuit, a pair of oscillator tubes connected together in push-pull relation, and another pair of oscillator tubes also connected together in pushpull relationship and generating oscillations approximately the same frequency as said first pair of tubes, the cathodes of said two pairs of oscillator tubes being connected together by a line efiectively a whole number of half wavelengths long, whereby predetermined phase excitation of each pair of oscillator tubes with respect to the other pair is obtained, two other pairs of oscillator tubes similarly connected together as said first two pairs, the cathodes of said last two pairs being connected to the cathodes of said first two pairs by a transmission line a whole number of half wavelengths long.

5. In an ultra short wavelength communication circuit, a pair of oscillator tubes connected together in push-pull relation, and another pair of oscillator tubes also connected together in push-pull relationship and generating oscillations approximately the same frequency as said first pair of tubes, the cathodes of said two pairs of oscillator tubes being connected together by a line eflectively a whole number of half wavelengths long, whereby predetermined phase excitation of each pair of oscillator tubes with respect to the other pair is obtained, said line having serially connected in each wire thereof a pair of condensers separated from each other by a distance of one-half wavelengths, each condenser being located from its nearest cathode by a distance of one-quarter wavelength.

6. In an ultra short wavelength communication circuit, a pair of oscillator tubes connected together in push-pull relation, and another pair of oscillator tubes also connected together in push-pull relationship and generating oscillations approximately the same frequency as said first pair of tubes, the grids of one pair of tubes being directly connected to the grids of the other pair of tubes through a Lecher wire system for obtaining a predetermined phase relation between said pairs of tubes.

7. In an ultra short wavelength communication system, a pair of oscillator tubes connected together in push-pull relation and another pair of oscillator tubes also connected together in pushpull relationship and generating oscillations of approximately the same frequency as those generated by said first pair of tubes, each of said tubes having an anode, cathode and grid, an antenna coupled to the grids of said first pair of tubes and another antenna coupled to the grids of said second pair of tubes, the cathodes of one pair of tubes being coupled to the cathodes of the other pair of tubes by a line having a predetermined length, whereby a desired phase excitation of each pair of oscillator tubes with respect to the other is obtained.

8. In an ultra short wavelength communication system, a pair of oscillator tubes connected together in push-pull relation, and another pair of oscillator tubes also connected together in pushpull relationship and generating oscillations of approximately the same frequency as those generated by said first pair of tubes, each of said tubes having an anode, cathode and grid, an antenna coupled to the grids of said first pair of tubes and another antenna coupled to the grids of said second pair of tubes, the grids of one pair of tubes being conductively coupled to the grids of the other pair of oscillator tubes by a line having a predetermined length, whereby a desired phase excitation of each pair of oscillator tubes with respect to the other is obtained.

GASTON MATHIEU. 

